Alloy



Patented May 21, 1935 NlTED STATES ALLOY Richard A. Wilkins, Rome, N.Y., asslgnor to Revere Copper and Brass Incorporated, Rome, N. Y., acorporation of Maryland No Drawing. Application March Serial No. 9,109-

3 Claims.

My invention relates to copper-base alloys. It will be understood thatthe yield point of an alloy, rather than its tensile strength, is thefactor which determines the maximum load to 5 which a part made of thealloy may be safely subjected. Also, it will be understood, the degreeof elongation, or ductility, of an alloy is the limiting factor inrespect to its suitability for many uses. Further, for economic reasonsit is essential that copper-base alloys be capable of being rolled anddrawn and otherwise worked both hot and cold, as copper-base alloyswhich can be worked only cold can be produced by mill processes only atso high a cost as to be pro- 0 hibitive for ordinary uses of the alloys,while copper-base alloys which can be worked only hot have so limited afield of usefulness, if any, as to be economically worthless. Obviouslytherefore copper-base alloys which may be worked both hot and cold, andhave both a high yield point and a high degree of ductility, are foreconomic reasons very desirable.

Heretofore, it has been attempted to secure alloys having'theseproperties by mixing copper, silicon and zinc, or copper, silicon andmanganese. It has been found however that the attempt to vary the yieldpoint in these alloys by varying the amount of either zinc, manganese orsilicon ordinarily results in an undesirable change in the ductility.The reason for this probably is because, to secure a hot and coldworkable alloy, the amount of zinc or manganese must be decreased whenthe amount of silicon is increased, and vice versa, with the result thatit is impossible with these prior alloys to regulate or vary the yieldpoint and at the same time secure the degree of ductility necessary tomake the alloys suitable for many commercial uses.

Applicant has found that if for the zinc, or manganese, smallpercentages of tin are substituted, and in. general the copper contentincreased, the yield point, by proper heat-treatment, may be variedwithout substantially affecting the ductility, and in many instancesslightly increasing the latter when the yield point is increased. Bymaintaining the amounts of tin and silicon within definite limits, andin proper proportion to each other, a hot and cold workable alloy isproduced. Within these limits and proportions, the yield point, tensilestrength and ductility may be varied by varying the amounts of bothsilicon and tin and by varying them in respect to each other. In allthese combinations the yield point of the cold worked metal iscontrollable through heat treatment.

Applicant has found that his improved alloys, as compared tocopper-siliconzinc and coppersilicon-manganese alloys, have a remarkablyhigh tensile strength and ductility when in both the fully annealed andcold worked condition, and when cold are susceptible of greaterreduction without annealing. For example, applicants alloys are capableof being reduced by cold rolling from 30 to without failure or it beingnecessary to anneal them during the reducing process. When fullyannealed all these alloys have a tensile strength of at least 58,000pounds per square inch and an elongation of at least 65% in two inches.All the alloys are capable of being cold drawn into rods having atensile strength of at least 120,000 pounds per square inch and anelongation of 10% in two inches, and are capable of being cold rolledinto sheets having a tensile strength of at least 110,000 pounds persquare inch and an elongation of 5% in two inches.

Applicants alloys also have the unique property of being capable of heattreatment to relieve cold working stresses without any material changein the tensile strength, ductility, or hardness and with a markedincrease in the yield point, whereas with copper-silicon-zinc andcopper-siliconmanganese alloys heat treatment to relieve these stressescommonly decreases the ductility at the expense of the tensile strength,yield point and hardness. For example, according to applicantsinvention, an alloy can be produced which may be cold drawn from thefully annealed condition in which it has a tensile strength of about61,000 pounds per square inch and an elongation of 75% in two inches toproduce a rod which has a tensile strength of about 136,000 pounds persquare inch, an elongation of 10% in two inches, a yield point of 88,000pounds per square inch, and a hardness number of about 94 Rockwell. Thisrod may be heat treated by heating it to about 500 to 600 F. for 30 tominutes and'slowly cooling it by exposing it to air at room temperature,and after heat treatment its tensile strength will be slightly increasedto about 141,000 pounds per square inch, its yield point markedlyincreased to 111,000 pounds per square inch, its elongation increased toabout 11% in two inches, and its hardness number to about 97 Rockwell.In other Words, this heat treatment at so-called relief annealingtemperatures, that is to say temperatures below recrystallizationtemperatures, secures a very marked increase in the yield point withoutreducing the tensile strength or hardness 01' materially affecting theductility.

Conveniently, the alloy may be fully annealed by heating it to a highertemperature, say 1000 to 1200 F., and it will be observed that when insuch condition, due to its very high ductility and susceptibility ofbeing greatly reduced by cold working without again annealing it, it maybe readily fabricated into articles having, as compared to articles madeof prior alloys, a high tensile strength, ductility, yield point andhardness,

after which the yield point may be very much increased by heat treatmentwithout destroying the high tensile strength, ductility and hardness.

Further applicant's alloys, when compared with copper-silicon-zinc andcopper-silicon-manganese alloys, have a greater corrosion resistancethaneither of these and have better welding properties than thecopper-silicon-zinc alloys.

Applicants alloys preferably contain 2.75 to 3.5% silicon. Below 2.75%silicon the alloys are deficient in tensile strength, although, fromthis aspect alone, in some instances the amount of silicon may be as lowas 2.25%. With above 3.5% silicon the alloys are economicallyunsatisfactory with respect to cold rolling and drawing properties andfor this reason are commercially undesirable.

The range of the amount of tin is a variable depending upon the amountof silicon employed. Throughout the entire range of silicon abovespecified alloys having the desired properties will be secured with aslittle as 0.25% tin. With any amount of silicon less than approximately3% the amount of tin should not exceed a value which is roughlyrepresented by a linear increase in tin from 1.8% to 2.25% silicon atthe rate of approximately tin for 1% increase in silicon, that is tosay, a linear increase in tin from 1.8 to 2% as the silicon increasesfrom 2.25 to 3.0% or a linear increase in tin from 1.9 to 2% as thesilicon increases from 2.75 to 3%. On the other hand, for any value ofsilicon more than 3% the amount of tin should not exceed a value whichis roughly represented by a linear decrease in tin from 2% at 3% siliconat the rate of approximately 43% tin for 1% increase in silicon, that isto say a linear decrease in tin from 2 to 1.7 %-as the silicon increasesfrom 3 to 3.5%. In other words, the maximum amount of tin that may beemployed for 3% silicon is 2%, but if the amount of silicon is increasedor decreased to above or below this value the maximum amount of tin thatmay be employed decreases approximately at the rate of for 1% increasein silicon and approximately at the rate of A% for 1% decrease insilicon.

With values of tin outside the ranges above defined for each value ofsilicon, the alloys will fail to possess one or more of the desirableproperties above mentioned, and if the alloys have amounts of tingreater than those indicated they will not be hot workable. Preferablythe amount of tin for the preferred range of silicon is approximately0.25 to 0.5% as within these ranges the alloys may be readily hot andcold worked and possess the peak values of the characteristic propertiesof the alloy. Also in these ranges the tin and silicon may be varied,each by itself or relative to each other, to control the yield point,ductility and tensile strength within limits suitable for commercialuses for which copper-base alloys of high tensile strength are employed.

Small amounts of certain metals may be present without affecting thedesirable properties of the alloy. For example, iron may be present invery small amounts without destroying any of the herein mentionedproperties of the alloy. The presence of aluminum should be avoided, assmall amounts even as low as 0.5% destroy the property of the alloy ofbeing susceptible of heat treatment for increasing its yield point.Aluminum in fact causes the alloys when heat treated to exhibit anincrease in ductility at a marked expense of their yield point, andfurther increases the difiiculty with which the alloys may be ho;worked. The alloys are substantially zincless, that is to say, they donot contain more zinc than values under 1%, as values of zinc under thisamount do not seem materially to affect the properties of the alloy. Foreconomic reasons it is dimcult to prevent the presence of fractions of apercent of zinc in copper-base alloys, and for this reason it may bedesirable, in order to produce a uniform product, to add small amountsof zinc to maintain a zinc content of say about 0.5%, as with this valueand other values under 1% the alloy is substantially zincless in so faras appreciable effects of zinc on the mentioned properties of the alloyare concerned.

I claim:

1. Substantially zincless copper-base alloys capable of being workedboth hot and cold, and capable when in the cold rolled and drawncondition of being heat treated at temperatures below recrystallizationtemperatures markedly to increase the yield point without reduction intensile strength and ductility, consisting essentially of copper,silicon and tin within the following approximate ranges and proportions:silicon 2.25 to 3.5%, tin 0.25 to 2%, balance substantially copper, theminimum amount of tin being 0.25% for all values of silicon, and themaximum amount of tin varying between 1.8 and 2% linearly and directlywith the silicon when the latter is between 2.25 and 3%, and varyingbetween 1.7 and 2% linearly and inversely with the silicon when thelatter is between 3 and 3.5%, the alloys being further characterized bya tensile strength of at least 55,000 pounds per square inch with anelongation of at least 60% in 2 inches when in the fully annealedcondition, and when in this condition being capable of being cold drawnto secure a tensile strength of at least 105,000 pounds per square inchwith an elongation of at least 9% in 2 inches or cold rolled to secure atensile strength of at least 100,000 pounds per square inch with anelongation of at least 4% in 2 inches.

2. The alloys according to claim 1 having 2.75 to 3.5% silicon.

3. Substantially zincless copper-base alloys capable of being workedboth hot and cold, and capable when in the cold rolled and drawncondition of being heat treated at temperatures below recrystallizationtemperatures markedly to increase the yield point without reduction intensile strength and ductility, consisting essentially of copper,silicon, and tin within the following approximate ranges andproportions: silicon 2.75 to 3.5%, tin 0.25 to 0.5%, balancesubstantially copper, the alloys being further characterized by atensile strength of at least 58,000 pounds per square inch with anelongation of at least 65% in 2 inches when in the fully annealedcondition, and when in this condition being capable of being cold drawnto secure a tensile strength of at least 120,000 pounds per square inchwith an elongation of at least 10% in 2 inches or cold rolled to securea tensile strength of at least 110,000 pounds per square inch with anelongation of at least 5% in 2 inches.

RICHARD A. WILIQNS.

CERTIFICATE OF- CORRECTION.

Patent No 2,002,460. I May 21, 1935.

RICHARD A. WILKINS.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,first column, line 26, ,for "to" read at; and that said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office.

Signed and sealed this 25th dayof June; D. 1935.

Br an M. Battey (Seal) Acting Commissioner of Patents.

